Saw blade with secondary teeth

ABSTRACT

A saw comprising a planar body includes at least one cutting edge with serrated teeth. The planar body has cutout portions displaced from the outer cutting edges which include sets of secondary teeth which are aligned generally parallel to or in an arc concentric with the outer cutting edge or edges.

CROSS-REFERENCE To RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISK APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

This invention relates to saw blades of the type generally used forcutting wood and other products. Such products may include lumber,layered wood products such as plywood or logs or posts, and non-woodproducts such as plastic, masonry and nonferrous metals.

The typical construction of a saw blade is a planar piece of metal withan outer cutting edge. The cutting edge typically contains serrationsarranged as forwardly inclined teeth. In circular saw blades thatoperate at very high speeds and with industrial bandsaws, the serrationsmay have hardened carbide tips.

Saw blades are planar but the serrations and teeth making up the workingedge of the saw blade generally protrude to either side of the plane ofthe blade. This defines the width of the cut of the blade or “kerf.” Thecutting action of the teeth produces chips and sawdust. These chips maybecome lodged in the kerf. It would be more efficient if there were someway to expel the chips as the blade advanced because the presence ofchips in the kerf means that the saw is working less efficiently andrequires more horsepower.

In addition, as the saw progresses deeper into the cut, more energy isexpended. There is more cutting product in the cut and consequently morefriction for the saw blade. Friction, in turn, creates heat and possiblyvibration. If the workpiece happens to vibrate at the correct frequency,there can even be breakage of carbide saw tooth tips.

Also, depending upon the number of teeth per inch, the pitch of theteeth and their overall size, the actual cut itself may be rough orsmooth. In some applications, it is desirable to have a very smoothsurface where the cut is made. In general however, in order to have asmooth surface, the teeth must be smaller and more numerous per lineallength, but this choice may require sacrificing both speed andefficiency.

In the past, circular saw blades have been designed which includedcutout squares placed along an interior diameter one hundred-eightydegrees apart with inserted carbide tips. This design was an attempt toprovide a means for clearing sawdust from the kerf but such designs haveproved unsatisfactory.

BRIEF SUMMARY OF THE INVENTION

A planar saw blade having an outer cutting edge with a plurality of sawteeth also includes sets of secondary teeth placed in cutout portionswithin the body of the saw blade. The secondary tooth sets provideportions within the body of the saw blade that provide additionalcutting action that reinforces the primary outer cutting edge of theblade.

BRIEF DESCRIPTION OF THE SEVERAL DRAWINGS

FIG. 1 is a side view of a circular saw blade employing a preferredembodiment of the present invention.

FIG. 2 is a side view of an alternative embodiment in a circular sawblade.

FIG. 3 is a side view of a further alternative embodiment of theinvention as used in a circular saw blade.

FIG. 4 is a side view of a fourth embodiment of the invention as used ina circular saw blade with an advancing workpiece shown in dashedoutline.

FIG. 5 is a partial cutaway side view of an embodiment of the inventionused in a bandsaw blade.

FIG. 6 is a side view of a handsaw employing the present invention.

FIG. 7 is a side view of a pruning saw employing the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a circular saw blade 10 has an outer perimeter 12.Distributed about the periphery of the outer perimeter are a number ofsaw blade teeth 14. Each of the teeth 14 have carbide tips 16. The blade10 is a planar piece of metal and includes arcuate cutout portions 18 a,18 b, 18 c and 18 d spaced 90° apart radially about an innercircumference of the blade 10 concentric with the outer perimeter 12.Each of the cutout portions 18 a, 18 b, 18 c and 18 d have a set ofsecondary teeth 20 a, 20 b, 20 c and 20 d respectively. Each of the setsof secondary teeth 20 a, 20 b, 20 c and 20 d have carbide tips,essentially the same as carbide tips 16 of the saw blade teeth 14. Eachset of secondary teeth 20 a, 20 b, 20 c and 20 d consist of four teeth,and the spacing between the teeth in each secondary set of teeth isapproximately the same as the spacing between the teeth 14 along theouter perimeter 12 of the blade 10.

The secondary cutting teeth 20 a, 20 b, 20 c and 20 d help the outerteeth 14 to cut more efficiently by providing a secondary cutting actionthat clears out chips that can fill the space occupied by the blade 10and by providing action along previously cut surfaces, smooths theopposing surfaces of the material cut by the primary saw blade teeth 14to make a finer, more finished cut.

FIG. 2 shows another circular was blade 22 having outer teeth 24 withcarbide tips. A plurality of sets of secondary teeth 26 a, 26 b, 26 cand 26 d are spaced 90° apart in cutout portions 27 a, 27 b, 27 c and 27d along an inner circumference of the saw blade 22. There are five teethin each of the sets 26 a, 26 b, 26 c and 26 d and these teeth have adeeper gullet and are spaced further apart than the primary teeth 24along the outer circumference of the blade 22. The difference betweenthis embodiment and the embodiment of FIG. 1 is that additional teeth ineach set with a different gullet between teeth is better for cuttinggreen lumber. The embodiment of FIG. 1 works best with dry lumber. Ingeneral, the denser the material, the more teeth that are needed in thesecondary set.

In FIG. 3, the saw blade 30 is designed for fine cutting action becauseit has a large number of teeth 32 about its outer perimeter. In the caseof blade 30, however, there are five sets of secondary teeth 34 a, 34 b,34 c, 34 d and 34 e which are spaced evenly 72° apart in arcuate cutouts33 a through 33 e about an inner circumference of the blade 30. Each ofthe sets of secondary teeth contains five teeth each and these teethhave deeper gullets and are spaced further apart than the primary teeth32. A greater number of sets of secondary teeth provides a finer cut orfinish to the edges of the material being cut.

The circular saw blade 30 has a center of rotation 31 and an outerradial edge 35. The outer radial edge has a plurality of saw teeth 32spaced uniformly a predetermined distance apart. Interior cutoutportions 33 a-33 e are spaced equal distances apart and lie generallyalong an inner circle concentric with the outer radial edge 35. Eachcutout portion has a second plurality of secondary saw teeth 34 a-34 e.All of the secondary saw teeth in each of the cutout portions have tipportions 37 arranged along a common arc also concentric with the outerradial edge and are thus radially equidistant from the center ofrotation 31 of the saw 30 as indicated by the dashed line.

Sometimes it is advantageous to include more than one secondary set ofteeth. Such an embodiment is shown in FIG. 4. In FIG. 4, a blade 40 isdesigned for a relatively fine cut because it has a large number ofprimary teeth 42 arranged about its outer perimeter 44. A first groupingof secondary teeth consists of secondary tooth sets 44 a, 44 b, 44 c, 44d and 44 e arranged in cutouts 43 a through 43 e. As in FIG. 3, thesecutouts are spaced 72° apart about an inner concentric circumference ofthe blade 40. To provide additional cutting action and a finer finish tothe cut, tertiary sets of teeth 46 a, 46 b, 46 c, 46 d and 46 e arepositioned in arcuate cutouts 45 a through 45 e along a second innerconcentric circumference spaced inwardly from the sets of secondaryteeth 44 a through 44 e. Like the secondary sets, the tertiary toothsets 46 a through 46 e each have five teeth. Each set of teeth 46 athrough 46 e is spaced 72° apart but is placed offset from the secondarysets in the radial gaps between each set of secondary teeth. Thisplacement properly balances the blade and maintains its structuralintegrity.

For each of the embodiments illustrated in FIGS. 1 through 4, theplacement of the sets of secondary saw teeth is determined by severalfactors. The sets of secondary saw teeth are distributed about animaginary circumferential arc which exists at a secondary radius whichis less than the outer radius of the blade itself. This secondary radiusmust be greater than the height of the material which is to be cut. Forexample, in a twenty-inch saw blade designed to cut a stack of pieces oflumber six inches high, the inner or secondary radius must be greaterthan six inches. As a practical matter, in order to preserve theintegrity of the blade, the radius should be greater than this andshould be longer than the height of the material to be cut by an inch ormore. For structural integrity, the secondary radius should usually begreater than half the distance from the center of the blade to its outerperimeter.

FIG. 4, for example, shows a workpiece 50 which may be a board or pieceof lumber having a height h. The workpiece slides along a table (notshown) in the direction of the arrow in FIG. 4 into the advancing teethof the saw blade 40. As shown in FIG. 4, the tertiary sets of teeth 46 athrough 46 e are placed evenly about an imaginary inner circumferencedefined by an inner radius “R” which has a dimension greater than theheight h of the workpiece 50.

Other factors influencing the number of secondary sets of teeth and thenumber of teeth per set include the thickness of the subject workpieceand its density. In general, thicker pieces of lumber require more setsof secondary teeth including tertiary sets of teeth and denser materialsrequire more sets of secondary teeth. Also, in general, the denser thematerial, the more teeth are required for each set. Thick green lumberwould be appropriate for the embodiment of FIG. 4 while thinner boardlumber or plywood might be more appropriate for the embodiment ofFIG. 1. In addition, more sets of teeth with more teeth per set areappropriate when a finer cut is desired. For example, in FIG. 3, thereare five sets of secondary teeth 34 a through 34 e with five teeth ineach set. This is due to the fact that the pitch of the teeth 32 of sawblade 30 is much finer than the pitch of the saw teeth in either FIG. 1or FIG. 2.

While the preferred embodiments have been described primarily inrelation to circular saw blades, the invention may be used on othertypes of blades as well. In FIG. 5, a bandsaw blade 52 includesoppositely opposed outer edges 54 and 56 respectively. Secondary toothsets are provided in cutout portions situated along the centerline ofthe blade 52. Secondary tooth sets 54 a and 54 b are oriented at thesame angle as the teeth of the outer edge 54 while secondary tooth sets56 a and 56 b have the same pitch and forward angle as outer edge 56.

Referring to FIG. 6, a handsaw 60 has a cutting edge 62 with a row ofserrated cutting teeth 62 a. Secondary toothed sets 64 are arranged instaggered fashion throughout the body of the planar saw blade 60 andextending generally parallel to the outer cutting edge 62.

Referring to FIG. 7, a pruning saw 70 includes a blade 72 having aserrated cutting edge 74 and three sets of secondary saw teeth 76.

As the examples of FIGS. 5, 6 and 7 show, the invention could be appliedto virtually any type of saw which includes a planar saw blade that iswide enough to provide space and has the structural integrity for cutoutportions which will support secondary sets of saw teeth.

For each set of secondary teeth illustrated in FIGS. 1 through 7, thereare a plurality of teeth in each set and the plurality of teeth all havea uniform pitch and a uniform gullet. There features greatly enhance thesaw's ability to expel chips and sawdust and make the blade cutsubstantially quieter.

1. A circular saw blade having a center of rotation and an outer radialedge, the outer radial edge having a plurality of saw teeth spaced afirst predetermined distance apart, a plurality of interior cutoutportions spaced equal distances apart and lying along a circleconcentric with said outer radial edge, each cutout portion having asecond plurality of secondary saw teeth, all of the secondary saw teethin each of the cutout portions having tip portions arranged along acommon arc and radially equidistant from said center of rotation.
 2. Thecircular saw blade of claim 1 wherein all of the secondary saw teeth ineach of the cutout portions are uniformly sized.
 3. The circular sawblade of claim 2 wherein said secondary saw teeth are uniformly spaced asecond predetermined distance apart, said second predetermined distancebeing greater than said first predetermined distance.
 4. A circular sawblade having primary saw teeth arranged along an outer peripherythereof, and having a plurality of interior cutout portions, each saidcutout portion having a plurality of secondary saw teeth wherein saidsecondary saw teeth are positioned along an arc concentric with saidouter periphery, wherein all secondary saw teeth are uniformly sized. 5.The circular saw blade of claim 4 wherein the primary saw teeth areuniformly spaced apart a first predetermined distance apart and thesecondary saw teeth are spaced uniformly within each cutout portion asecond predetermined distance apart wherein said second distance isgreater than said first distance.